The present invention relates to a wall structure for a combustion chamber, more particularly such a wall structure which minimizes turbulence to the cooling air passing along an inner surface of the combustion chamber wall.
It is known from U.S. Pat. No. 3,899,884 to Ekstedt to construct a gas turbine combustion chamber in an annular configuration having inner and outer walls bounding the annular combustion chamber. The combustion chamber is surrounded by an outer housing spaced outwardly from the outer wall of the combustion chamber. The combustion chamber wall comprises a plurality of segments with an upstream end of one segment being located outside and overlapping a downstream end of an adjacent segment. The overlapping portions of the adjacent segments define a space which communicates through at least one main cooling air hole with the space between the combustion chamber and the outer housing. The space also has an outlet such that the air passing through the at least one main cooling air hole into the space will exit substantially tangentially to an inner surface of the adjacent downstream wall segment to cool the inner surface of the combustion chamber. The wall segments also define holes for the primary combustion/dilution to enable the air to pass into the combustion chamber and be mixed with fuel to form a combustible mixture.
As a general rule, such combustion chamber walls define diverse holes to allow the introduction of the requisite air flows into the combustion chamber. The air is required for combustion (through intake holes for primary air and/or dilution air) and to introduce air adjacent to the walls of the combustion chamber to cool the walls during the ongoing combustion process (cooling air intake holes).
In known techniques, the air forms cooling films on the inner surface of the combustion chamber walls (i.e. that surface facing the interior of the combustion chamber) on either side of the primary air intake holes. The positions of the dilution air intakes are typically determined by factors relating to the performance, stability, efficiency and temperature of the combustion chamber.
As a rule, the primary and dilution air intake holes are orifices having widely flanged edges to provide good guidance to the air entering the combustion chamber. Such orifices are difficult to manufacture when the parts of the combustion chamber structure must be machined. Also, the manufacture of such combustion chamber orifices requires the maintenance of a rather large distance between the orifices and the downstream air cooling film.